1. Field of the Invention
It is desired to provide an effective cooling aerosol spray formulation which does not contain halo-substituted solvents such as chlorofluorocarbon compounds (CFCs) or chloro-substituted compounds. European Patent Application 404334 seeks to provide such. an aerosol formulation based on organic solvents without CFCs and proposes particular blends of certain petroleum distillates in the formulation. Although such products go some way to satisfy concerns regarding flammability, it is desired to improve the non-flammability properties of the formulations still further, particularly in respect of the residue of the product remaining on the skin after administering the spray.
We have now found that we can provide a water-based aerosol formulation with improved non-flammability properties. The presence of water considerably improves the non-flammability properties and also provides a spray formulation having valuable cooling properties with a fast onset of action combined with a sustained cooling effect. We have overcome the problem of combining the propellant (which is necessary in formulations adapted for aerosol use) in a water-based formulation as a single phase. Thus we have been able to produce a homogeneous mixture including water with dimethyl ether as propellant for aerosol use. The aqueous single phase aerosol spray formulation according to the present invention comprises dimethoxymethane, dimethyl ether and an alcoholic co-solvent. The formulation has been achieved without any halogenated component.
2. Description of the Prior Art
Other aqueous based aerosol formulations have also been proposed, however, they are associated with a number of disadvantages. For example, UK Patent Application 2008611A proposes a self-propellant spray system for use in cosmetics, for room treatment and/or in medicine, comprising a mixture of active compound, carbon dioxide, dimethyl ether, water and either methylene chloride or 1,1,1-trichloroethane. However, this composition still requires the use of chlorinated solvents. Japanese Patent Application No. 56135414 proposes an aerosol type antiinflammatory analgesic formulation comprising as propellants liquid petroleum gas and dimethyl ether and as a liquid phase, specified active ingredients, alcohol and water. However, the cooling effect on the skin is achieved by the selection of three of the particular four active ingredients specified. European Patent Application 414920A proposes a cooling formulation in the form of a sherbet-type foam. This may be messy to use and the cooling effect is much reduced when the foam is applied to dressings covering the affected area. U.S. Pat. No. 4716032 proposes an aqueous-based cooling spray for preventing mastitis in cows comprising a mixture of propellant (such as dimethyl ether), water, a disinfectant and other listed components including a C.sub.1-3 alkanol and an emollient. However, a satisfactory cooling effect for use in accordance with the present invention would not be achieved due to the high level of water present.